Core drilling apparatus



June 25, 1963 R. J. DU BERGER 3,095,050

CORE DRILLING APPARATUS Filed April 2, 1962 2 Sheets-Sheet 1 R. J. DU BERGER CORE DRILLING APPARATUS June 25, 1963 2 Sheets-Sheet 2 Filed April 2, 1962 United States Patent 3,095,059 CORE DRHLING APPARATUS Roland Joseph do Berger, 108A 8th Ave., Calgary, Alberta, Canada Filed Apr. 2, 1262, Ser. No. 184,181 Claims priority, application Canada Feb. 15, 1962 3 Claims. (Cl. 175-254) This invention relates to improvements in core drilling apparatus, and is especially concerned with a core cutting mechanism.

After a drill string has been operating for some time and has cut a core which has entered the inner barrel of the drill string, it is necessary to sever the core from the parent rock adjacent the drill bit, so that, when the drill string is withdrawn from the bore, it can lift the free section of core up to the surface for disposal.

The present invention is concerned with a core cutting mechanism designed to play its part in the carrying out of such an operation. More specifically the invention is concerned with a core cutting mechanism that can be made to operate automatically on reversal of thrust in the drill string.

This object is achieved by providing a core cutting mechanism comprising (a) .An annular housing,

(b) A circumferentially arranged series of cutters in said housing having cutting edges facing radially inwardly,

(0) Means mounting each cutter in said housing to be movable between a radially outwardly withdrawn position and a radially inwardly projecting position,

(d) A ball associated with each cutter mounted to project therefrom radially inwardly of the series,

(e) Each cutter including cam surfaces cooperating with its associated ball for controlling movement of the cutter whereby thrust in a first axial direction on the balls relative to the housing maintains the cutters in withdrawn position and thrust in the other axial direction on the balls relative to the housing forces the cutters to projecting position.

One manner of carrying the invention into practice is illustrated by way of example in the accompanying drawings. For convenience, the present invention has been shown employed in conjunction with a novel construction of a drill string, the features of which form the subject of companion patent application of even date Serial No. 184,180.

'FIGURES 1A to 1C are continuations one of the other that together serve to make up a longitudinal central section of a drill string assembly.

FIGURE 2 is a horizontal section of the drill string assembly of FIGURE 1 showing the core cutting mechanism on line II'II of FIGURE 1.

FIGURE 3 is a section on IIIII-I in FIGURE 2.

FIGURE 4 is a fragment of FIGURE 3 showing the positions of the parts of the core cutting mechanism during drilling.

FIGURE 5 is a similar fragment showing the action of .the parts of the core cutting mechanism when the drill string is withdrawn.

The drawings show outer core barrel sections :10, connectcd together by barrel couplings 11 and terminating at the lower end in a core barrel bit stabilizer 12 to which there is screwed a diamond bit 13. At the upper end, the core barrel section 16 is connected to a top adaptor section 14. Each of the outer sections .10 has secured to it an inner core barrel section by suitable fixing means such as set screws 16. Further, inner core barrel sections 17 are similarly secured within barrel couplings 11, and inner core barrel section 18 is similarly secured within bit stabilizer 12, with core cutter housing 19 posi tioned between barrel section 18 and bit :13. The set screws fixing sections 17 and 18 to the outer members 11 and v12 are not visible in the drawing because they are disposed around the structure away from the plane on which the drawing section is taken. They are conventional in nature and similar to the set screws 16 that are shown. The core cutter housing 19 is held in place by the bit 13 which holds the housing up against the bottom edge of the barrel section 18. -At .the top end of the string, inner core section 15 has mounted on it a ball type check valve 20 that will permit flow of gas or liquid up out of the core space defined by the inner faces of the inner core sections, but will check any tendency for return flow.

Situated in the walls of the inner sections 15 and spaced apart from each other both longitudinally and circurnferentially are balls 21 mounted as free turning bearings in retaining supports 22 in such a manner as to project out into the core space.

An annular housing 19 contains the core cutting mechannism which is the subject of the appended claims, and which comprises a plurality of balls 23 distributed circumferentially around the housing 19. Each ball 23 is held free running within a groove formed by lips 19a on housing 19 and cooperates with an associated cutter 24 that is freely pivotally mounted on a pin 25. Each cutter 24 has a cutting edge 26. When the apparatus is drilling (depicted in FIGURE 4) the thrust on the drill string is downward in relation to the rock core 27. Each ball 23 is thus urged upward by the core 27 to act on cam surface 28 of its cutter 24 to withdraw-cutting edge 26, and permit smooth downward movement of the drill string over the core. The balls 23 act as bearings during this movement, similarly to balls 21.

When the thrust on the drill string is reversed, as withdrawal of the string from the bore commences, balls 23 are drawn down by the core 27 and urged against cam surfaces 29, as demonstrated in FIGURE 5. This movement forces the cutting edges 26 out into contact with the core 27 sufliciently to sever the core from the parent rock, since the drill string is still rotating. The core fractures across in a like manner to glass once a crack has been started. The upper surfaces of cutters 24 then engage the end of the severed core to lift it out of the bore.

Each ball 23 is thus permitted a small range of travel in the axial (up and down) direction, while being retained against escape from its associated cutter.

I claim:

1. For use in core drilling appartus, a core cutting mechanism comprising:

(a) an annular housing,

(b) a circumferentially arranged series of cutters in said housing having cutting edges facing radially inwardly,

(0) means mounting each cutter in said housing to be movable between a radially outwardly withdrawn position and a radially inwardly projecting position,

(d) balls mounted in said housing, each ball bearing against an associated cutter and each ball projecting radially inwardly from said housing,

(e) each cutter including a pair of cam surfaces against which its associated ball bears for controlling movement of the cutter, whereby thrust in a first axial direction on the balls relative to the housing urges each ball against a first said cam surface of its associated cutter to maintain the cutters in withdrawn position and thrust in the other axial direction on the balls relative to the housing urges each ball against a second said cam surface of its associated cutter to force the cutters to projecting position.

2. A core cutting mechanism according to claim 1,

wherein said cutters are each freely pivotally mounted about a pin extending through said housing generally tangentially thereof.

3. -In core drilling apparatus, a drill string assembly comprising (a) barrel means having an inner cylindrical face de fining a core space, (b) means for rotating said barrel means, 7 (c) a drill bit secured to an end of said barrel means to form a core, (d) and .a core cutting mechanism secured to said barrel means near said barrel end to rotate therewith, (e) said core cutting mechanism comprising (i) a circumferentially arranged series of cutters each having a cutting edge facing radially inwardly, (ii) means mounting each cutter to be movable between an inoperative withdrawn position and an operative projecting position in which said cutting edge projects into the core space to engage a core therein, (iii) halls mounted in said mechanism, each ball bearing against an associated cutter and each ball projecting into said core space to bear against a core therein,

(iv) each cutter including a pair of cam surfaces against which its associated ball bears for controlling movement of the cutter, whereby upward thrust of a core on the balls during drilling urges each ball against a first said cam surface of its associated cutter to maintain the cutters in inoperative position and reversal of thrust during withdrawal of the drill string urges each ball against a second said cam surface of its associated cutter to force the cutters to projecting position to sever a core in the core space.

References fitted in the file of this patent UNITED STATES PATENTS 

1. FOR USE IN CORE DRILLING APPARATUS, A CORE CUTTING MECHANISM COMPRISING: (A) AN ANNULAR HOUSING, (B) A CIRCUMFERENTIALLY ARRANGED SERIES OF CUTTERS IN SAID HOUSING HAVING CUTTING EDGES FACING RADIALLY INWARDLY, (C) MEANS MOUNTING EACH CUTTER IN SAID HOUSING TO BE MOVABLE BETWEEN A RADIALLY OUTWARDLY WITHDRAWN POSITION AND A RADIALLY INWARDLY PROJECTING POSITION, (D) BALLS MOUNTED IN SAID HOUSING, EACH BALL BEARING AGAINST AN ASSOCIATED CUTTER AND EACH BALL PROJECTING RADIALLY INWARDLY FROM SAID HOUSING, (E) EACH CUTTER INCLUDING A PAIR OF CAM SURFACES AGAINST WHICH ITS ASSOCIATED BALL BEARS FOR CONTROLLING MOVEMENT OF THE CUTTER, WHEREBY THRUST IN A FIRST AXIAL DIRECTION ON THE BALLS RELATIVE TO THE HOUSING URGES EACH BALL AGAINST A FIRST SAID CAM SURFACE OF ITS ASSOCIATED CUTTER TO MAINTAIN THE CUTTERS IN WITHDRAWN POSITION AND THRUST IN THE OTHER AXIAL DIRECTION ON THE BALLS RELATIVE TO THE HOUSING URGES EACH BALL AGAINST A SECOND SAID CAM SURFACE OF ITS ASSOCIATED CUTTER TO FORCE THE CUTTERS TO PROJECTING POSITON. 